What's a function and what's functional failure?

A function clearly describes what a piece of equipment is intended to do, as well as the level of performance expected to result. Functional failures, on the other hand, detail all the conditions that would prevent a piece of equipment from operating at peak performance. Today's businesses that understand functions and functional failures will be able to establish and improve reliability-centered maintenance programs.

Understanding the Nuances of Failure

Many organizations tend to look at equipment or process failure as an either/or situation. If a machine is working, then there is no need to worry. If a machine is not working, that is considered a failure. Maintenance technicians are called in when equipment stops working. This leads to a simple, yet often inefficient, program of reactive maintenance.

In reality, functional failures should not only encompass complete breakdowns, but also they should address any issues that are outside the normal functioning of a piece of equipment or process.

The trouble with this more nuanced definition, however, is that normal function is difficult to clearly explain. If you asked different people in your organization how a piece of equipment should normally function, you might get varying answers.

Example of Functional Failure Analysis

Functional failure analysis can be performed on just about any piece of equipment or process. For example, let's look at a piece of equipment that is designed to maintain a discharge flow of 500 gpm plus or minus 10 percent.

A few functional failures that can be identified with such a piece of equipment might be an inability to discharge flow at all, a situation where the fluid flow is restricted, a failure to contain fluid, or a discharge flow that falls outside of the specified range.

All of these situations would be considered functional failures for this particular piece of equipment. Things like sensors and industrial IoT can help provide ongoing monitoring of possible functional failures and report these situations to a centralized computer system.

Next Steps: Create a Better Condition Monitoring Program

Once you have defined functional failure statements for your critical assets, you can create a better condition monitoring program. Many common patterns are found within functional failures and these can often be anticipated with a solid preventive maintenance program or even a predictive maintenance program.

Remember to consider functional failures throughout the entire lifecycle of a piece of equipment beginning with its initial design and ending at its decommissioning. Both crisis and chronic failures should also be taken into account.

After functional failures are defined, companies should move on to thinking about failure modes. In our example, our asset may need to be shut down completely if there is no discharge flow. However, if the fluid flow is simply restricted or falls out of the ideal range, a simple work order can be issued without shutting down the asset.

Be Thorough in Functions and Functional Failure Analysis

It's always tempting within an organization to implement programs like this quickly. However, dealing with functional failures warrants a diligent effort to ensure that both functions and functional failure lists are complete.

Bring in those team members who can help you put together a complete list of intended functions of each piece of critical equipment. Once you understand all the functions of an asset, it will be easier to list functional failures. Make sure you have a complete account of all your failure modes, including hidden failures.

Don't forget to take into account safety, health, and environmental risks. You need a solid understanding of your performance standards for each piece of equipment or process. Once you have those components in mind, you'll be able to identify which type of maintenance program would best serve that piece of equipment or process.